1. Field of the Invention
This invention relates to hydrolytically stable aromatic tetraphosphites and their use as antioxidants in organic materials such as organic polymers.
2. Description of the Prior Art
Phosphites are used in organic polymers and other organic materials as antioxidants. The phosphites are generally considered better than phenolic antioxidants at high temperatures because they eliminate hydroperoxides which decompose and lead to autooxidation chain reactions. Thus, phosphites are important for oxidative stability during various operations including polyolefin extrusion.
Phenolic and phosphite antioxidants are often used together in polyolefin homopolymers and copolymers to provide antioxidant protection for both low and high temperature exposure. Unfortunately, additional expense is encountered as additives in larger amounts are needed for the polymers. Thus, there exists a need for effective antioxidants at a reasonable additive price, not only for polyolefins, but other substrates as well.
It is common practice to include an antioxidant in organic materials normally susceptible to oxidative degradation. Many of the antioxidants employed have limited effectiveness or tend to impart undesirable properties to the organic material such as causing color. The problem is particularly acute with polymers and copolymers of ethylenically unsaturated monomers, especially polyolefins such as polyethylene or polypropylene. These materials are subjected to elevated temperatures during processing, which tends to destroy many antioxidants with the result that the polymer rapidly degenerates during use. The compounds of the present invention allow organic materials to maintain excellent color and thermal stability.